Water drainage and flood risk for the Parish of St Clement

WQ.69/2026

WRITTEN QUESTION TO THE MINISTER FOR INFRASTRUCTURE

BY DEPUTY K.M. WILSON OF ST. CLEMENT

QUESTION SUBMITTED ON MONDAY 2nd MARCH 2026 ANSWER TO BE TABLED ON MONDAY 9th MARCH 2026

Question

"Will the Minister advise what surface-water drainage and flood-risk assessments, if any, have been carried out for the Parish of St.Clement over the last five years, and for each assessment detail any –

1. identified gaps or vulnerabilities; and
2. mitigation work undertaken or proposed, including timelines and costs?"

Answer

The approach to surface water drainage and flood-risk assessments is not done on a Parish-by-Parish basis, but  more  on  a  holistic  view for the  Island. Surface  water  naturally  makes  its  way  over  Parish boundaries, creating a joint liability if the network is not sufficiently maintained and enhanced.

Over the past five years, the following Government assessments have included consideration of the impact on the Parish of StClement:

1. Jersey Strategic Flood Risk Assessment (SFRA, 2021)

The SFRA provides an islandwide assessment of surface water, drainage exceedance and tidal flood risk, including climate change impacts. StClement is fully represented in the mapping and risk analysis. The SFRA identifies surface water accumulation and overland flow routes, alongside a strong dependence on pumping stations where high tides restrict outfall discharge.

2. Bridging Liquid Waste Strategy (LWS, 2023–2026)

The  Bridging  LWS  modelling  covers  all  parishes  and identifies drainage  capacity  limitations, rainfall hotspots and  hydraulic pinch  points,  providing  the  evidence  base  for future flood mitigation projects,  including  in  StClement,  with  the  existing  surface  water  catchment described in Section 7 of that document.

3. Government of Jersey Surface Water Management Plan (SWMP, 2023)

The  2023  SWMP  updates  the  island's  hydraulic  model  and  assesses  inland  pluvial  flooding  and climate change impacts across 25 high risk "Hot Spot" areas. Although StClement is not a Phase 1 hotspot, the  SWMP  forms  the  technical  basis  for identifying local  drainage  undercapacity,  rainfall  response and flood risk mapping that applies across the island. StClement will be assessed in the Phase 2 hotspots, which include areas hydraulically linked to StClement such as Georgetown, La Rocque, Samares, Le Bourg and Le Rocquier.

Gaps and Vulnerabilities Identified

From the SFRA:

• Surface water exceedance is the key risk, driven by intense rainfall and local overland flow pathways.

• Tide locking of outfalls during high tides increases reliance on pumping stations to prevent inland flooding.

 From the Liquid Waste Strategy (LWS):

• Le Hocq and Pontac Pumping Stations, both built in 1968, have ageing spun-iron rising mains and limited surge capacity, making them sensitive to storm inflows.

• Saline intrusion creates septicity and accelerates corrosion, threatening operational reliability during high-risk storm tide conditions.

Mitigation Work Undertaken (2019–Present)

Mitigation works that have been undertaken since 2018 have been included as some works have been completed just outside of the requested timeframe but have equal importance to flood mitigation measures.

Pontac Pumping Station (2022) – Mechanical and electrical upgrades delivered. Cost: £75,000.

Telemetry and Monitoring Upgrades (2021–2023) – Modern telemetry installed across the pumping network, including StClement, improving real time flood response. Cost: £150,000, allocated in 2022.

Baudrette Brook Archimedes Screw Upgrade (~2019) – The Baudrette Brook Pumping Station serves the wider eastern coastal drainage system. Its two 9.75–10m Archimedes screws were replaced after 50 years of service, at a cost of £713,000.

These works remain directly relevant today due to the long (30–50+ year) design life of Archimedes screws, providing reliable drainage to the eastern seaboard and indirectly supporting hydraulic performance along the StClement frontage.

Development  Control  Measures  (2021) –  Post SFRA,  new  developments  are required to provide site specific Flood Risk Assessments (FRAs) and  incorporate Sustainable Urban Drainage Systems (SUDS) to avoid increasing runoff into parish drainage networks.

Mitigation Proposed (Medium Term)

Surface water improvements: These are guided by the SWMP and will continue to be programmed as capital schemes through the Infrastructure Rolling Vote, however, funding in this area remains a challenge.

Coastal Flood Risk Management for StClement

Coastal flooding is an increasing hazard that also impacts surface water performance due to tide locking.

Havre des Pas Coastal Flood Alleviation Scheme:

The Government's major coastal defence scheme will deliver a one in 200-year standard of protection (including sea level rise) and will directly benefit approximately 850 metres of StClement coastline within the  next ten years (subject to capital funding), reducing overtopping, improving outfall reliability and strengthening community and utility resilience.

Future Eastern Coastal Works (from 2040):

The coastal frontage east of Millar d's Corner is scheduled for improvement from 2040, in line with the Shoreline Management Plan's climate change sequencing.

In addition to the strategic work detailed above, there is the day-to-day management of the surface water network for which we have dedicated teams. They undertake programmes of maintenance for our drainage assets  to  ensure  they  continue  to operate at  their optimum capacities,  with  both  remote  monitoring technology and manual checks in place to alert our Operations teams to any issues where additional action, such as over pumping or clearing of blockages are required. Prior to all major road resurfacing schemes, drainage assets are inspected to ensure that defects are addressed.

Relations with the Parish of St Clement are excellent, with regular communication and joint problem- solving helping to ensure a continuity of service. Later this month, meetings are scheduled with Parish of St  Clement  officials  and  representatives  from  the  farming  community  and Government  of  Jersey's Environment department to discuss the impact of field run-off on the road drainage network.

All road authorities are responsible for maintaining the drainage assets on their roads.

In  summary,  StClement's  inland  flood  risk  has  been  assessed  through  the  SFRA  and  SWMP, which identify vulnerabilities in drainage capacity and aged pumping infrastructure. Upgrades have been delivered  at  Le Hocq, Pontac and Baudrette Brook,  with  further  renewals  planned. Coastal flood risk management  through  the  Havre  des  Pas  scheme  will  provide  significant  added protection, improving both coastal and inland flood resilience for the Parish, subject to funding. The continued maintenance and monitoring of the network will continue to alleviate flood risks but only with increased funding levels will we be able to begin combating the challenges posed by climate change.